Calculation of photon scattering and transmission correction factors for a free air ionization chamber at Nuclear Science and Technology Research Institute in Iran

Abstract In primary standard dosimetry laboratories, the air kerma strength of low energy brachytherapy sources 125 I and 103 Pd is measured by standard free air ionization chambers. At present, one of these free air ionization chambers is constructed in Radiation Application Research School, in Nuclear Science and Technology Research Institute in Iran. The transmission and scattering correction factors are needed for the absolute determination of air kerma strength. Transmission and scattering correction factors were calculated for a monoenergetic point isotropic source with energies from 5 keV to 100 keV for ionization chamber with 4 cm and 6 cm aperture radii by using the MCNP 4C code. The calculated scattering correction factors for 125 I and 103 Pd brachytherapy sources are 0.9987 and 0.9992, respectively and determined transmission correction is one for our free air ionization chamber of aperture radius 4 cm.